There are many applications where it is either necessary or advantageous to join a first component around a second component. When the components are made of metal, welding is a commonly employed joining technique. The heat affected zone produced from welding may, however, adversely affect the material properties of the components being joined. In the case of hardened bearing steel, for example, the heat affected zone severely reduces material hardness, which is a vital property of components like the rings of rolling element bearings.
An alternative technique is to join a first component around a second component by means of a plastic flow joint. One example of this technique is disclosed in U.S. Pat. No. 4,249,298, in which an outer member (e.g. flywheel) is joined to an inner member (e.g. shaft boss) by means of a connecting ring. A circumferential groove is formed on connecting surfaces of both members, and axial recesses are formed on an inner surface of each circumferential groove. Then, the connecting ring is placed between the inner and outer members. Finally, the connecting ring is pressed and plastically deformed such that material of the ring flows into the grooves and recess.
Because a maximum gap between the two connecting surfaces is greater than a thickness of the connecting ring in undeformed state, the connecting ring needs to be made from a malleable material, so that it can radially expand under compression to fill each circumferential groove and radially lock the inner and outer members. Copper, brass, aluminium and soft iron are mentioned as suitable materials for the connecting ring. These metals have a relatively low yield strength in comparison with e.g. steel. Iron, for example, has a yield strength of approximately 50 MPa, while carbon steels have a yield strength of 250-1300 MPa. The method of joining disclosed in U.S. Pat. No. 4,249,298 is therefore not suitable for components which, in use, are subjected to high axial loading, since the joint must then possess a high shear strength.
Consequently, there is room for improvement.